time.minutes-between

pub fn minutes_between(start_date: &str, start_time: &str, end_date: &str, end_time: &str) -> i64

fune!(time.minutes-between@^1);  // then call minutes_between(…)

use super::funejson::Value;  ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::dates_add_days::epoch_day_from_iso;  ← from dates.add-days ^1.0.0 · built alongside by fune

fn minute_of_day(time: &str) -> i64 {
    let b = time.as_bytes();
    let ok = b.len() == 5 && b[2] == b':' && [0, 1, 3, 4].iter().all(|&i| b[i].is_ascii_digit());
    let digit = |i: usize| i64::from(b[i] - b'0');
    let (hours, minutes) = if ok {
        (digit(0) * 10 + digit(1), digit(3) * 10 + digit(4))
    } else {
        (-1, -1)
    };
    if !ok || hours > 23 || minutes > 59 {
        panic!("\"{}\" is not a time of day (HH:MM, 00:00 to 23:59)", time);
    }
    hours * 60 + minutes
}

/// Minutes from one local date and time to another: the difference between two
/// wall-clock readings. It knows nothing of time zones or daylight saving, so
/// across a clock change it differs from real elapsed time by the change.
///
/// # Panics
/// Panics on a malformed date or time.
pub fn minutes_between(start_date: &str, start_time: &str, end_date: &str, end_time: &str) -> i64 {
    let days = epoch_day_from_iso(end_date) - epoch_day_from_iso(start_date);
    days * 1440 + minute_of_day(end_time) - minute_of_day(start_time)
}

pub fn fune_vector(args: &[Value]) -> Value {
    Value::Int(minutes_between(
        args[0].as_str(),
        args[1].as_str(),
        args[2].as_str(),
        args[3].as_str(),
    ))
}

Install

fune build

With that line in your source, in a Rust project (language rust in fune.project), fune build resolves it and its 1 dependency, pins them in fune.lock, downloads only the Rust package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. A crate’s build.rs runs it before every compile. Or pin a range in fune.project and build in one step:

fune add time.minutes-between

The manifest, vectors and README with only the Rust implementation. Install it without the registry with fune add ./time.minutes-between-1.0.0-rust.fune, or fetch it from a terminal with fune pull time.minutes-between@1.0.0:rust.

The whole function, every language, is one file too: time.minutes-between-1.0.0.fune, 8,862 bytes, sha256 f28512233b8908b71542c3178abccb2281cb736b93ba1f13ac1eede9c71e9386. It installs into a project of any language.

// fune: before time.minutes-between

// fune: after time.minutes-between

// fune: replace dates.add-days in time.minutes-between

// fune: step time.minutes-between after <n|label>

More from the author

**Local wall-clock time, no time zones.** Both times are read off the same clock on the wall, and the answer is the difference between those readings. It does not know about daylight saving: in the UK, 00:30 to 03:30 on 29 March 2026 is 180 minutes here though only 120 minutes passed, because the clocks went forward at 01:00; on 25 October 2026 the same readings are 180 here and 240 in reality. Payroll and time-and-attendance rules differ on which of those to pay, so this capability does not pick one silently: if real elapsed time matters, convert both instants to UTC with a time zone database first and subtract those.

Times are strictly HH:MM, 24-hour, 00:00 to 23:59. "24:00", "9:00" and "5pm" are errors rather than guesses; the end of a day is 00:00 on the next date.

Files